Minesweeper

Instructions

Your task is to add the mine counts to empty squares in a completed Minesweeper board. The board itself is a rectangle composed of squares that are either empty (' ') or a mine ('*').

For each empty square, count the number of mines adjacent to it (horizontally, vertically, diagonally). If the empty square has no adjacent mines, leave it empty. Otherwise replace it with the adjacent mines count.

For example, you may receive a 5 x 4 board like this (empty spaces are represented here with the '·' character for display on screen):

·*·*·
··*··
··*··
·····

Which your code should transform into this:

1*3*1
13*31
·2*2·
·111·

Additional jq command line options

You'll notice extra options for jq in the tests.

run jq -s -R -c -f minesweeper.jq << 'END_INPUT'

What are they?

• -s

  This is "slurp" mode. Instead of handling the input as a stream of JSON objects, all the input will be slurped into an array.

  $ seq 5 | jq -c '.'
  1
  2
  3
  4
  5
  $ seq 5 | jq -s -c '.'
  [1,2,3,4,5]
  

• -R

  You may have seen -r already, to output "raw" strings (without quotes). This is the opposite. Each line of input is taken to be a string.

  Two examples:

  $ seq 5 | jq -R -c .
  "1"
  "2"
  "3"
  "4"
  "5"
  
  $ echo 42 | jq '. * 2'      # input is a JSON number
  84
  $ echo 42 | jq -R '. * 2'   # input is a JSON string
  "4242"
  

When you put these two options together, you don't get an array of strings: you get the entire input as a single string, including end-of-line newlines.

$ seq 5 | jq -s -R -c .
"1\n2\n3\n4\n5\n" 

Handling this is part of the challenge of this exercise.